Un-compromising a compromised iPhone?

I have a friend (don’t laugh, it's true!). My friend has an iPhone, which he believes has been compromised.

He says that he's been researching this sort of thing on the Internet, and his phone exhibits a lot of classic signs:

His battery has started draining really quickly

His call's keep on getting dropped, even in areas of good reception

He often hears a "click" sound when he's in the middle of a conversation (he says it sounds like someone else has picked up – just like in the old days when you had multiple telephone handsets in a house all sharing the same line).

Most telling of all, he says that his phone can be sitting on his desk when it suddenly "wakes up" (the screen lights up) but there's no call. My friend says he believes this indicates that someone may be remotely accessing his text messages and emails.

This sort of thing is taken much more seriously in Europe. Over here in America, however, if you talk to the folks at your service provider they tend to tell you that nothing is wrong (as they usher you out of the door).

I really don’t know much about this sort of thing (my coverage with AT&T is so poor that I rarely get any phone calls at all, which suits me to the ground).

My friend's questions can be summarized as follows:

Is there any way to determine if your iPhone has been compromised?

Is there any way to "de-compromise" your iPhone?

If the only way to fix things is to reload the iPhone's IOS (operating system), what's the best way to save all of your content (Apps, Photos, Music, and Contacts) and then reload it later?

Any advice you can give would be very much appreciated.

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Q: Is there any way to determine if your iPhone has been compromised?
A: Not for normal people.
The "typical" symptoms listed on the web are unreliable.
And the software tools that detect jailbreaking are easily fooled and unreliable.
Q: Is there any way to "de-compromise" your iPhone?
A: A factory reset (IOS reload) will fix software compromises that reside on the phone.
Hardware compromises require a new phone.
Network compromises require a new carrier.
(http://en.wikipedia.org/wiki/Greek_wiretapping_case_2004%E2%80%932005)
Q: If the only way to fix things is to reload the iPhone's IOS (operating system), what's the best way to save all of your content (Apps, Photos, Music, and Contacts) and then reload it later?
A: iTunes
In the future, never leave the phone unattended
and never loan it to anyone.
And/or plan on frequent OS reloads.

http://www.eetimes.com/electronics-news/4407957/Eight-great-hacks-I-want-to-see-at-DesignWest-2013?pageNumber=1
According to the link above it doesn't seem to ridiculous anymore, especially when they hold conferences showing how to do it.